The present invention relates to a pneumatically or electromotively operable disc brake, having a brake caliper, which reaches around a brake disc, at least one brake application device for applying the disc brake by way of a displaceably guided element, in particular a crossmember. The displaceably guided element has at least one threaded hole, into which an adjusting spindle is screwed which bears a pressure piece, with which it is possible to press a brake lining against the brake disc. An adjusting device, which is operatively connected to the adjusting spindle for adjusting the clearance play, and a securing element, which acts on the adjusting spindle so as to impede rotation up to a defined torque, are also provided
In a disc brake of this type, as is known, for example, from DE 94 22 342 U1, a rotary lever acts on a crossmember (also known as a bridge or transverse member), in which preferably two adjusting spindles are mounted, which each have a pressure piece for accommodating a brake lining which is pressed against a brake disc during braking operations. The two adjusting spindles are provided with an external thread and are screwed, in each case, into a threaded hole of the crossmember.
By using an adjusting device which is assigned to one of the adjusting spindles, and by use of a driver of the other adjusting spindle, the brake pad is applied by rotation of the adjusting spindles in the threaded holes in the event of wear of the brake lining to such an extent that the play (or gap) between the brake lining and the brake disc always remains substantially constant.
In order to prevent that, as a result of vibrations during driving operation, the adjusting spindles change their position undesirably, and thus the distance between the brake lining and the disc brake, that is to say the play, securing elements are used. The securing elements act on the adjusting spindles so as to impede rotation, with the result that the above-mentioned unintended displacement is prevented. Here, the securing elements are in frictional contact with the adjusting spindle or parts of the latter. The frictional force is dimensioned such that the rotation of the adjusting spindles is possible without problems in the event of a defined torque which is to be applied by the adjusting device, said torque being greater than that which can result from the vibration forces during driving operation.
Similar problems occur in the case of purely static intermittent operation of the brake as a result of tumbling of the adjuster drive with respect to the adjusting members (threaded tubes or adjusting spindles), specifically if a can also be adjusted so as to be constant as far as possible over time and loading. Precisely this is possible only to a limited extent in the prior art.
A known securing element therefore comprises a (secondary) seal, which is arranged in an end region of the adjusting spindle that faces the pressure piece, and which engages into the adjusting spindles in a securing manner.
Inter alia for the function of impeding rotation, the secondary seal or the part which engages into the adjusting spindle is composed of an elastomer such as silicone rubber, which is integrated into the secondary seal.
In particular during heavy usage, the adjusting spindles reach temperatures which a plastic securing element cannot resist in the long term.
Embrittlement and aging of the material and reactions to the unavoidable action of grease also limit the service life, with the result that wear-induced replacement is necessary at intervals which make little economic sense.
Although solutions are known in which metallic rings or tongues, which are inserted into the crossmember, come into engagement with the adjusting spindles, this construction can in general be realized only with special mechanical machining of the crossmember, which naturally has the consequence of an increase in the manufacturing costs.
The present invention is therefore based on the object of developing a disc brake of the above-mentioned type such that a long service life of the securing elements is attained with structurally simple means. It also is intended mechanical machining of the crossmember, which naturally has the consequence of an increase in the manufacturing costs.
The present invention is therefore based on the object of developing a disc brake of the above-mentioned type such that a long service life of the securing elements is attained with structurally simple means. It also is intended to be possible to realize fixing of the limiting torque, up to which the securing elements prevent undesirable rotations of the adjusting spindles, which fixing is as precise as possible and is constant over the service life.
This object is achieved by a disc brake wherein the securing element is configured as a spring ring having at least one or more spring clips, which are distributed over the circumference and are in frictional contact with the adjusting spindle outside the internal thread of the displaceably guided element, in particular of the crossmember.
One particular advantage consists in that it is possible for the limiting torque to be defined exactly, which limiting torque is in addition very constant over the long term and up to which rotations of the adjusting spindle or spindles are prevented.
The structural configuration selected also results in a long list of advantages, both with regard to the operation of the disc brake and also with regard to the manufacture of the securing elements and with regard to their mounting.
In particular, the capability of easy retrofitting to existing disc brakes is to be mentioned.
In order to define the limiting torque up to which rotations of the adjusting spindle or spindles are prevented, it is possible, in particular, to vary the type and number of spring clips. At least one spring clip is preferably provided. However, an arrangement having three or more, in particular five or six, spring clips is more advantageous, as the spring clips may firstly still be arranged satisfactorily on the ring element and secondly ensure a uniform force action on the adjusting spindle or spindles from a plurality of points.
In addition to the friction surface which may be selected with regard to its dimensions, it is also possible to define the rotational impeding by defining the spring force, the spring force resulting from the restoring force of the individual spring clips and their number.
The spring ring, preferably composed of spring steel, may be manufactured from a simple, stripshaped punched part, which is to be shaped with low complexity by being bent to form a circular ring. Here, the two ends are preferably configured (for example, in the manner of a lock) in such a way that they engage into one another in a form-fitting manner when plugged together.
It is likewise not necessary to machine the crossmember, as the spring ring is arranged outside the internal thread of the crossmember in the region of the secondary seal, that is to say on the side which faces the pressure piece, and its spring clips, which are preferably configured as spring arms, are in frictional contact there with the adjusting spindle.
In an advantageous manner, the available installation space may thus be utilized for the insertion of the spring ring; it is to be emphasized as a particular advantage that the spring ring may also be installed without problems as a replacement into existing disc brakes, that is to say brakes which are already in operation. Here, the available assembly tools can be used for retrofitting or replacement. The simple assembly with the equally unproblematic attachment to the brake likewise leads to a reduction in costs, such as the ability to be manufactured using known technologies.
The spring ring which is, as has been mentioned, preferably metallic may be subjected to high temperatures compared with a spring ring made from plastic, with the result that the operating temperatures which occur do not have any effects on the service life of the component. A contribution is also made by the fact that a spring ring of this type is extremely robust mechanically, that is to say it is not sensitive to the loading which occurs, as a result of which a long service life is attained. It is possible here to manufacture the spring ring from stainless spring steel.
It is also contemplated to design the spring ring in an integrated manner with a seal. Here, it is also possible for the spring ring to be surrounded completely or partially by injection-molded and/or foamed encapsulation. Here, the spring clips are preferably left free from the foamed encapsulation. It is possible in this way to manufacture, for example, a secondary seal, for example so as to complement a folding bellows as a primary seal, which protects the interior of the brake caliper against ingress of moisture.
The spring arms may be shaped differently, for example U-shaped in their free end region, the open side pointing outward, that is to say away from the adjusting spindle. Shaping of this type affords particular advantages during assembly, that is to say when the spring ring is pushed onto the adjusting spindle (retrofitting), or during the assembly of the threaded spindle on a conveyor belt if the spring ring is already situated on the crossmember (original equipment).
The width of the spring clips, in particular in the region of contact with the adjusting spindle, is dimensioned such that the spring clips bear against a plurality of crests of the threads.
As an alternative to a slotted ring, which can be manufactured very easily, the spring ring may also, in principle, be of a closed configuration.
In summary, the following advantages result from the securing element of the present invention, in particular:
it can be subjected to high temperatures
it is mechanically robust;
it is elastically deformable;
it is suitable for a long service life;
it is corrosion-resistant;
it can be inserted in the available installation space;
it can be encapsulated by the injection molding of plastic;
it can be retrofitted;
it can be replaced;
it can be manufactured inexpensively;
it can be attached to the brake simply; and
it can be assembled simply in series production and onsite in the event of a replacement or retrofitting.
Further advantageous configurations of the invention are described and claimed herein.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.